Mpod s/w device states and transitions

The device state transition diagram (STD) implemented is shown below, where ovals are states, boxes are transitions, and diamonds are branching points. The colours used follow those used in the GUI client. Note that the ERROR state can be reached from any state or transition and the lines to it are not shown.

LV or HV channel states and transitions

The state of a channel is driven by setting operator or switch to the appropriate value (e.g. to ‘on’ or 1, ‘off’ or 0, respectively) and not, as in the s/w device, by pressing a button to start a transition. Despite this difference the same diagram elements are used to show the the channel STD, but using orange fill of a box to indicate a property change.

The STD shown is for the case where autoRearm is False and latched interlocks on HV channels must be cleared by pressing the Clear interlocks button.

If autoRearm is True, the latched interlock is cleared automatically thus aligning it to LV channel interlock behaviour and it is sufficient to enter ‘off’ or 0 at the operator or switch switch to go to OFF. Clearly, if the interlock condition (signal) is still being applied then the channel state will return immediately to INTERLOCKED without going through OFF.

The channel’s state if UNKNOWN if the channel f/w bit status does not correspond to a real state - this has never been observed and is not interpreted as an ERROR.

The ERROR state is set if the channel is tripped, current limited, etc., when the reason is shown in stateInWords. Additionally on disable the poll loop is terminated, all channel states are set to ERROR and the schema is kept. The latter is driven by the requirement of seeing the last state of device and channels, on enable the schema is rebuilt.